Transactions Volume 1-4

Transactions Volume 1-4

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1880 edition. Excerpt: of any object he removed the middle lens, for, he writes, " the fewer the refractions the clearer and brighter the object appears." An account of Eustachio Divino's Microscope was read before the Royal Society, in 1668. It consisted of an object-glass, a middle (field) glass and a compound ocular in which two plano-convex lenses were placed with their convex surfaces touching each other (being thus very similar to " Ramsden's Positive Eye-piece " sometimes used for micrometric work at the present day.) The tube in which these glasses were contained is said to have been as large as a man's leg, and the eye-glasses as broad as the palm of a man's hand--measurements which, though rather vague for strict accuracy, are yet sufficiently suggestive to convince one that it must have been a rather formidable affair. It had four different lengths, giving magnifying powers of 4r, 90, III and I43 times, respectively. In 1690, Philip Bonani published an account of his microscopes, the second being remarkable as the first exainple of the use of a rack and pinion for adjustment of focus, and of a substage condensor for improving the illumination. Improvements were constantly being made in the construction and mounting of simple microscopes; the greatest, perhaps, being that of Dr. Nathaniel Lieberkuhn, of Berlin, about 1740, which consisted in placing the lens in the centre of a highly-polished concave speculum, by means of which a strongly concentrated illumination is reflected upon the upper side of the object, thus rendering it possible to examine small opaque objects with comparatively high powers, a thing impossible before, as, by reason of the short working distance of simple microscopes, the proximate sides more

Product details

  • Paperback | 178 pages
  • 189 x 246 x 10mm | 327g
  • United States
  • English
  • black & white illustrations
  • 1236993446
  • 9781236993441